A pair of alleged Islamic terror plots uncovered this week in Germany and Denmark share some disturbing hallmarks: Officials link both to al-Qaida and have found tentacles stretching all the way to Pakistan, the likely hiding place of Osama bin Laden.

The schemes -- which could have caused massive loss of life -- have been a chilling reminder to Europeans of the threat they still face due to porous borders, restive minorities and perceived allegiance to the United States.

Analysts and security officials warn that terrorists could be gearing up ahead of the anniversary of the Sept. 11 attacks, with German authorities saying the investigation there was aided by the suspects' increased activity ahead of the anniversary.

"It is possible that a certain motivation (of the plotters) can be attributed to this anniversary," said German Federal Prosecutor Rainer Griesbaum -- though he added there was no concrete evidence yet of a link.

Wolfgang Bosbach, a key member of Chancellor Angela Merkel's governing Christian Democratic Union, told N-24 television: "When you leaf through a calendar, it's only a matter of hours until Sept. 11."

Three people were arrested in connection with the German plot, all allegedly trained at a camp in Pakistan, and all linked to the al-Qaida-influenced Islamic Jihad Union. Eight othersare under investigation. German authorities said those arrested shared a "profound hatred of U.S. citizens," and U.S. officials said Frankfurt International Airport and America's Ramstein Air Base were among the targets.

On Tuesday, eight men -- of Pakistani, Afghan, Somali and Turkish origin -- were arrested in Denmark. Authorities said the men were linked to senior al-Qaida leaders, but have not revealed what their targets were, or when they planned to strike.

Al-Qaida leaders including bin Laden and his No. 2, Ayman al-Zawahri, have frequently threatened to strike Europe in audio and video warnings. Anti-terror experts have said recently that the pace and speed of those warnings has picked up in recent months, leading to speculation that al-Qaida's inner circle is in greater control than once believed.

While Europe and the United States have diverged -- often sharply -- on issues such as Iraq, the creation of the U.S. holding facility at Guantanamo Bay, Cuba, and the CIA's use of secret prisons for terror suspects, it is Europe that has found itself the victim of more terror attacks since Sept. 11.

The most serious strikes, aimed at commuters in Madrid in 2004 and London in 2005, killed 243 people between them. There have been many more schemes -- some of them monstrous in scope -- that have failed to come off.

Analysts say tensions over the publication of cartoons of the Prophet Muhammad deemed offensive by many Muslims, as well as a lack of opportunities and sense of marginalization in Muslim communities, have put Europe squarely in the cross-hairs of radicals. Porous borders and years of relatively open immigration policies have added to the problem, they say.

Robert Sturm, an Austrian terrorism expert, said Europeans are deceiving themselves if they think their countries are not potential targets, or that opposition to the war in Iraq means that they are immune.

"We are part of the danger zone," he said, adding that counterterrorism officials are trying to determine whether the German incident was part of a wider plot to attack targets across Europe.

Tadeusz Wrobel, an analyst of military and security issues in Warsaw, Poland, said all European nations are targets, regardless of their involvement in Iraq, because Islamic radicals "treat the whole Western world as their enemy."

Many of those arrested in recent years have been homegrown terrorists, often from large, sometimes disenfranchised Muslim communities, and the recent arrests seem to follow the pattern. Two suspects arrested in Germany were citizens who had recently converted to Islam, while the third was of Turkish origin. Six of the Danish suspects were citizens, and the other two had residence permits.

Bob Ayres, a former U.S. intelligence officer who is now an analyst at Chatham House, a London think tank, said the foiled plots should serve as a wake-up call.

"The Europeans have thought this was exclusively a problem between the U.S. and the Islamic world," he said, adding that the continent is suffering now because of lax immigration policies and a failure to integrate newcomers. "People haven't realized that the radical Islamists embrace an ideology that transcends national loyalties. They're not Germans, Brits or French. They are radical Muslims living in these countries."

Louis Caprioli, of the risk management firm Geos, and former assistant director of the DST, France's counterterrorism agency, said security officials were taking special note of the Sept. 11 anniversary, but added that anniversaries have so far not been marked by attacks.

"Sept. 11 is in the minds of all terrorists, and all targets," he said. "(But) the threat is permanent."

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An unidentified man believed to be a terror suspect, is led away by masked police, at the German Federal Court in Karlsruhe, southern Germany, Wednesday, Sept.5, 2007. Authorities said Wednesday they had arrested three suspected Islamic terrorists from a group with "profound hatred of U.S. citizens" for plotting imminent, massive bomb attacks on U.S. facilities in Germany. (AP Photo/Michael Probst)